1. Field of the Invention
The present invention relates to an image reader and, more particularly, to an image reader which uses a one- or two-dimensional array image sensor of a solid state imaging element such as a CCD as an image reading means, and which forms an image of a recording medium on a light-receiving region of the sensor and scans the optical image by the sensor in a main or primary scanning direction and a subscanning or secondary scanning direction so as to generate a time-serial electrical pixel signal as a reading signal.
2. Description of the Prior Art
An image reader of this type is well known as an image reader of, e.g., a microfilm.
FIG. 7 schematically shows an arrangement using a one-dimensional array image sensor.
Referring to FIG. 7, a microfilm (roll microfilm, microfiche film, microstrip film or the like) is provided at a film illuminating position 2 between a film illumination lamp device 1 and an imageing optical system 3 along an optical axis L. A horizontally arranged one-dimensional array image sensor 4 is subscanned by a drive mechanism (not shown) along a Y--Y direction as a subscanning direction perpendicular to an X--X direction as a main scanning direction. A light-receiving region 5 is defined by a main scanning length and a subscanning movement length of the sensor 4.
A frame f of the microfilm F to be read is automatically aligned at the illuminating position 2 by an automatic search mechanism. A blip mark m for searching is performed on the film F and is detected by a mark detection unit 6. Alternatively, the film F is manually aligned. The frame f at the illuminating position 2 is illuminated by the illumination lamp device 1, and an image of light transmitted through the film i.e., an image of the frame f is formed within the light-receiving region 5 of the sensor 4 by the optical system 3. The optical image f' is sequentially read from the upper to lower side by electrical main scanning along the X--X direction and mechanical subscanning movement along the Y--Y direction. Then, a time-serial electrical pixel signal S as a reading signal is generated from the sensor 4.
The output signal S is supplied to an image reproducing device or an image display device such as a printer mechanism, a facsimile receiver, a display device or the like, or a recording device or the like, thus being subjected to reproduction, display, storage and the like of an image corresponding to the original image.
An image to be read is moved with respect to the fixed one-dimensional array image sensor so as to perform subscanning (slit exposure subscanning).
When a two-dimensional array image sensor is utilized, an image of the film is formed within a two-dimensional light-receiving region, and is read by electrical main scanning and subscanning of the sensor itself, thereby similarly generating a time-serial electrical pixel signal as an image reading signal.
As for microfilms, among any of a roll microfilm, a microfiche film, a microstrip film and the like, the respective image frames f- are formed on a film surface in a vertical posture or mode, as shown in FIG. 8(a), and are formed thereon in a lateral mode, as shown in FIG. 8(b).
Th image reader shown in FIG. 7 is used for reading an image formed in the vertical mode. When the image of the film F is in the vertical mode, the optical image f' of the corresponding image frame is formed in a vertical state within the light-receiving region 5 of the sensor 4 by the optical system 3. Therefore, the main scanning and subscanning reading of the optical image f', i.e., the image frame by the sensor 4 can be sequentially performed from the upper to lower side of the vertical image. Thus, there is no problem in image display or copy by a reproducing apparatus such as a CRT display or a printer.
However, when the film F is in the lateral mode, the optical image f' of the image frame is formed by the optical system 3 laterally with respect to the light-receiving region 5 of the sensor 4, as shown in FIG. 9. As a result, the main scanning and subscanning reading of the optical image f', i.e., the image frame by the sensor 4 is performed using one long side as an upper side and the other long side as a lower side. For this reason, the following drawbacks are presented:
(1) The reproduced image on the CRT display or the printer is laterally formed, resulting in inconvenience.
(2) In many cases, since left and right side portions a of the lateral optical image f' fall outside of the light-receiving region 5, and the image in the out-of-range portions a cannot be read and reproduced, thus preventing practical use.
When images are formed on a microfilm while a posture angle of an object is inclined with respect to a camera, the image frames f are formed on the film F at the inclined posture angle, as shown in FIGS. 10(a) and 10(b).
(3) Such an image frame in an inclined posture is formed as the optical image f' on the light-receiving region 5 of the sensor 4, as shown in FIG. 11. When the inclined posture image f' is main scanned and subscanned by the sensor 4, the reproduced image is also inclined. When an inclination angle is large, portions b of the optical image f' fall outside of the reading range.
Even when the image frame f is formed on the surface of the film F in the vertical or lateral posture, if the direction of a film set in the image reader or a film holding carrier is shifted from a correct direction, the optical image f' of the image frame f is inclined with respect to the light-receiving region 5 of the sensor 4 as shown in FIG. 11.
The drawbacks (1), (2) and (3) are common to an image reader for performing slit exposure subscanning processing by moving an image of a film with respect to a fixed one-dimensional array image sensor and to an image reader using a two-dimensional array image sensor when a microfilm having image frames in the vertical mode is used in an image reader for reading image frames in the lateral mode.